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CGI Setup

HTML If you want to implement CGI using Java (without violating the assignment rules), you can create a standalone Java CGI script that generates HTML output. This script will be executed by Apache, similar to how a compiled C binary would work.

1. Write a Java CGI Program (HelloCGI.java)

This Java program does not use any networking functions—it simply prints an HTML response.

import java.io.*;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class HelloCGI {
    public static void main(String[] args) {
        // Get current time
        LocalDateTime now = LocalDateTime.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy HH:mm:ss");
        String formattedTime = now.format(formatter);

        // Print HTTP headers
        System.out.println("Content-Type: text/html\n");

        // Print HTML response
        System.out.println("<html>");
        System.out.println("<head><title>CGI with Java</title></head>");
        System.out.println("<body>");
        System.out.println("<h1>Hello from Java CGI!</h1>");
        System.out.println("<p>Current Time: " + formattedTime + "</p>");
        System.out.println("</body>");
        System.out.println("</html>");
    }
}

2. Compile the Java Program

Run the following command in VS Code’s terminal to compile the program:

javac HelloCGI.java

This creates HelloCGI.class, which is the compiled bytecode.

3. Run and Test the Output in VS Code

To check if the output is correct, run:

java HelloCGI

Expected output:

Content-Type: text/html

<html>
<head><title>CGI with Java</title></head>
<body>
<h1>Hello from Java CGI!</h1>
<p>Current Time: 03-02-2025 14:35:12</p>
</body>
</html>

4. Deploy the Java CGI Script to Apache

If you want to run this through a web server, do the following:

Move the Java Class to Apache’s CGI Directory

  1. Copy HelloCGI.class to the Apache CGI directory:

    sudo cp HelloCGI.class /var/www/html/cgi-bin/

  2. Ensure the CGI script is executable:

    chmod +x /var/www/html/cgi-bin/HelloCGI.class

Modify Apache Configuration for Java CGI

  1. Open Apache’s configuration file:

    sudo nano /etc/apache2/apache2.conf  # Ubuntu/Debian
sudo nano /etc/httpd/conf/httpd.conf # CentOS/RHEL

  2. Enable Java CGI Execution by adding this inside the <Directory> block for /cgi-bin/:

    AddHandler cgi-script .class

  3. Restart Apache:

    sudo systemctl restart apache2  # Ubuntu/Debian
sudo systemctl restart httpd    # CentOS/RHEL

5. Test the Java CGI Script in a Browser

Open your web browser and go to:

http://your-server-ip/cgi-bin/HelloCGI.class

It should display the generated HTML page with the current time.

Key Points

✅ No networking functions—this strictly follows the assignment rules.
✅ Uses standard Java features (no external libraries).
✅ CGI-compliant—works like compiled C binaries.
✅ Can be tested in VS Code first, then deployed to Apache.